Amplitude modulation system



April 8, 1952 J. M. VILLEMAGNE AMPLITUDE MODULATION SYSTEM Filed May 8,1950 INVENTOR JEAN M. VILLEMAGNE Q BY ATTORNEY Patented Apr. 8, 1952AMPLITUDE MODULATION SYSTEM Jean Marie Villemagne, Paris, France,assignor to International Standard Electric Corporation, New York, N.Y., a corporation of Delaware Application May 8, 1950, Serial No.160,755

In France June 3, 1949 3 Claims. (01. 332-44) The present inventionrelates to very wide frequency band amplitude modulation devices,particularly those providing carrier suppression.

In known modulating devices, there is obtained generally in the outputbesides modulation products; currents comprising either the carriercurrent or the modulating current or combinations of these currents andof their harmonics. When it is necessary to obtain pure modulationproducts, filters have been employed, in the output of the modulatingdevice which introduce undesirable effects, such as different phaseshifting at different operating frequencies, etc.

One of the objects of the present invention is to provide an amplitudemodulation device with a very wide frequency band which delivers in itsoutput only modulation products, without the need for the use offilters.

Another object of the present invention is to provide a multiplierdevice in which the two voltages to be multiplied play effectively thesame role in order to obtain an output voltage which is effectivelyproportional to the two input voltages.

7 According to a feature of the invention, there is provided atranslation system comprising two pairs of rectifiers, a first means forapplying a sinusoidal voltage in push-pull to each pair of rectifiers, asecond means for applying a sinusoidal voltage in push-pull to each pairof rectifiers in the same sense as the first means with respect to onepair of rectifiers but in the opposite sense with respect to the otherpair of rectifiers, and a pair of output terminals each terminalconnected to the output of one pair of rectifiers.

The above-mentioned and other features and objects of this invention andthe manner of attaining them will become more apparent and the inventionitself will be best understood, by reference to the followingdescription of an embodiment of the invention taken in conjunction withthe accompanying drawings, wherein the single figure is a schematicdiagram of a system for combining signals which may be used either as amodulator or as a frequency enerator.

In the drawing there is shown four vacuum tubes of the pentode type i,2, 3 and 4 and adjustable resistances 5, 6, l and 8 and a fixedresistance 9 used for adjusting the working conditions of the saidtubes.

The mid-point I2 of the secondary winding of transformer II is connectedto a biasing battery l3. lThe terminal l4 of the secondary winding 10 oftransformer II is connected by means of a resistance [5, on the one handto the control grid I6 of pentode 4 and on the other hand to the controlgrid ll of pentode 2; the terminal I8 of the secondary winding l0 oftransformer H is connected by means of resistance 19 on the one hand tothe grid 20 of pentode l and on the other hand to the grid 2| of pentode3. The mid-point 22 of the secondary winding 23 of transformer 24 isconnected through a resistance 25 to the positive terminal of a hightension battery 26. The terminal 21 of secondary winding 23 of thetransformer 24 is connected on the one hand to the grid 28 of pentode 3and on the other hand to the grid 29 of pentode 4. The terminal 30 ofthe secondary winding 23 of transformer 24 is connected on the one handto the grid 3| of pentode 2 and on the other hand to the grid 32 ofpentode l. The anodes 33 and 34 of pentodes l and 4 are connected to theterminal 35 of the primary winding 36 of transformer 31. The anodes 38and 39 are connected to the terminal 40 of the primary winding 36 oftransformer 31. The midpoint 4| of the primary winding 36 of transformer31 is connected to the positive terminal of the high tension battery 26.

The arrangement having been described, its operation is as follows: if asinusoidal voltage is applied to the primary winding 42 of transformer II it will be seen on the drawing that the pentodes l and 2, 3 and 4 actas the vacuum tubes of two push-pull sets or pairs placed in oppositionand no current is then obtained in the secondary winding 43 oftransformer 37. The same result is obtained when the primary winding oftransformer 24 is fed with a sinusoidal current. On the contrary if twosinusoidal voltages, such as a carrier wave and a modulating wave, arerespectively applied to the terminals 44 and 45 of the primary winding42 of transformer II and to the terminals 46 and 41 of the primarywinding 48 of transformer 24, it follows from the fact these voltagesare applied by means of the circuits described above, to different gridsof each one of the pentodes I, 2, 3 and 4 that there is obtained in theoutput of transformer 31 a modulated current comprising only the sidebands, the carrier frequency and the modulation frequency having beeneliminated by the operation of the circuits placed in opposition.

If there is applied to the primary windings 42 and 48 of the twotransformers H and 24 the same sinusoidal voltage, there is obtained inthe secondary winding 43 of transformer 31 the second harmonic of theinput current to the device which in this case operates as a multiplier.

It is obvious that the transformers II and 24 may be replaced byoutphasing tubes as well known in the art.

While I have described above the principles of my invention inconnection with specific apparatus, it is to be clearly understood thatthis a ment of each tube, a second means for applying a sinusoidalvoltage balanced with respect. to. ground in push-pull to each pair oftubes. in the; same sense as the first means with respect to one pair oftubes but in the. opposite sensewith re-- spect to the other pair oitubes, said second means including connections. to. another controlelement of each tube, said firstand. second means: including connectionsto ground, andapair: of output terminals, each terminal connected: tothe output of onepair'of tubes.

2; A- translation system according: to claim 1 further including aplurality of adjustable resistant elements, at least one of saidresistant elements being inserted in series in the connections from eachof said cathodes to ground.

3. A frequency multiplier comprising two pairs of rectifiers, a firstmeans for applying a sinusoidal: voltage. inpush-pull' to each; pain ofrectifiers, a=second means for applying the-same-sinusoidal voltage inpush-pull to each pair of rectifiers in the same sense as the firstmeans with respect to one pair of rectifiers but in the opposite sensewith respect to the other pair of rectifiers, and a pair oi'output.terminals each terminal connected to; the. outputrn". one pair ofrectifiers.

JEAN MARIE VI-LLEMAGNE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES- PATENTS Number Name Date.

2,239,376 Brunrr Apr..29, 1941 2,275,020 Purington Mar..3,,19422,484,107 Maron: Oct. 11, 1949

